Here’s the second half of Floyd Hyatt’s post on Complexity in the Novel.
Some of the more important aspects (to Fantasy world builds) are:
A consistent magical system, if used.
Again, like in a game, the strength, movement ability, advantages and limitations of any piece need to be set down. Limits need to be set on the use, and on the extent, or means by which the “physics” of the magical system may operate. Ideally, the system should incorporate a sense of balance, of Peter paying Paul, where for every gain, there is a consequent cost. Superman needs kryptonite, else there can be no practical conflict that he could not win, thus no story tension or point. Such systems need to be internally consistent.
A historical background, whether propounded or alluded to.
Worlds do not exist in a vacuum. They have history, a logical course of development. An over-all conflict No society is perfect. There are stories in the newspapers every day. Again, whether yours focuses on one of these or not, the reader should remain aware that in the background, life is happening.
A political and social reality
This goes without saying, but whether this aspect needs to be writ large or small will (or should) depend on your story focus.
Everything has a physical, or at least, sensible, presence. Is that town to the north, or was it west? Is that world of yours frigid, or like Dune, a desert world? What about its structure, if anything, might affect its inhabitants’ growth, society, politics, appearance?
Science fiction builds face similar challenges. While some venues highlight marvelous devices, mechanics, and physics, still all the above elements apply and, in the end, most modern SF tales are character-driven stories, writ upon the backdrop of the imagined world, and the focus is likely only on particular parts that the characters must deal with, surmount, or find a way to live with.
The trick is, once these features are worked out, how much detail in each respect is absolutely required to carry out your plot. Is it really necessary to envision that blue ice-cream makes babies cry? That the mayor’s fifth cousin, twice removed, has an adopted child? That the planet has one point oh six more degrees of axial tilt than Earth? And even if it is, can the story be told without reference to this? Try to keep your chess board as uncluttered as possible. After your story is writ, such non-essentials as seem to enrich, without interfering with the clarity of your story, can be added in, for color or further depth. These elements can only enhance a good story; they won’t putty over its flaws.
On the other hand, an involved reader will invest a little work to follow a good story’s logic, and some forms do focus on presenting the reader a Rubik cube as the plot itself. But it is probably smarter for the author not to depend on background complexity to carry the story
WRITING PROMPT: A character in a fantasy stops in a food shop. The other customers are dressed differently than he or she is. The waitstaff treats him or her differently than the other customers. The amount and/or quality of the food he or she is served is different and the bill is higher or lower. Describe this is such a way as to SHOW something about the world or events around the scene.